Detonation/Spark Knock/Pings

Definition: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening. Sounds like popcorn popping.

^ Check EGR System for proper operation. See Chart C-7C.

^ Check vacuum sensor hose for fuel in hose or restrictions, and vacuum sensor for high output.

^ Check ignition timing. See Vehicle Emission Control Information label.

^ Check for obvious overheating problems. Use ALCL tool if available. 85~C-100~C (185~F-215~F) is normal (Calif).

- Low coolant:

- Loose water pump belt.

- Restricted air flow to radiator, or restricted water flow thru radiator.

- Inoperative electric cooling fan circuit.

^ Check for air leaks at carburetor mounting and intake manifold.


^ Check for poor fuel quality, proper octane rating.


^ Check TPS enrichment operation. See Chart C-2F.


^ Remove carbon with top engine cleaner. Follow instructions on can.


^ If excessive carbon in cylinders, check for leaking valve seals.


^ Check for incorrect PROM (Calif.).


^ Check for improper operation of transmission (i. e. ,linkage adjustment) and TCC. Use ALCL tool if available (Calif).